1. Field of Invention
This invention relates to a flux-captivated flyback transformer which may be used in horizontal sweep circuits for CRTs used in video terminals, for example, and it also relates to a method of reducing very low frequency transmissions in a flyback transformer.
2. Background Information
Most all electronic circuits produce some electromagnetic emissions (EMI) at some levels. Personal computers, used in today's workplace, have cathode ray tubes (CRTs) that are used as video display terminals (VDTs) to enable operators to communicate with the computers. These VDTs are accused of causing psychological and physiological problems when operators use the VDTs for extended periods of time. As a precautionary measure, certain countries have developed stringent guidelines regulating electromagnetic emissions from the VDTs.
A major source of electromagnetic field emissions relates to horizontal scan circuitry which controls the position of an electron beam in the CRT. A flyback transformer that is used in the horizontal scan circuitry is the principal cause of the EMI. The flyback transformer produces the high voltage which drives the electron beam mentioned.
There have been various efforts to design the flyback transformers so that the emissions that they generate are minimized. Some of these efforts include various types of shields and additional windings to offset some of the emissions mentioned.